sequences and series - Finding hte value of $1/(1^2)+1/(2^2)+1/(3^2)+dots +1/(n^2)$

Sorry, my English isn't quite well.

Here is the problem.

When $n$ moves toward infinity
$$
1/(1^2)+1/(2^2)+1/(3^2)+\dots +1/(n^2)=?
$$

Any ideas?